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Adding a relay for the ignition circuit
https://slantsix.org/forum/viewtopic.php?t=53910		 Page 1 of 1
Author:  killnine [ Wed Nov 20, 2013 11:27 am ]
Post subject:  Adding a relay for the ignition circuit
70 Duster, slant six, EI.

So I've come across some issues with my under dash wiring. I should start by saying that I have an immediate need to get the car running, which is driving some of my decisions. I'm all for doing things right, but right now, I need to do the things that will lead to a running car that is safe.

I've got voltage drops on just about every part of the ignition system under the hood, except the wiring coming from the battery or the starter relay feeding the bulkhead. Based on my research, what this means is that the return from under the dash is where things are going wrong.

I don't have time to tear the dash apart and fix things at the moment. I'm limited in tools and work area, and the car is probably riddled with black widows since it was sitting in Oklahoma for about 3 years.

It has run, and ran well, for at least 10-15 minutes at a time. At some point I got a melted alternator battery output terminal.

The PO bypassed the ballast resistor, but has a can style red coil installed. If I had known this could cause damage I would have fixed it first thing, but it is what it is.

When testing under the dash, everything I can get to in the ignition switch wiring and the main feed coming from the ammeter are all dropped by about 2 volts. I suspect the ammeter connections of the dash side of the bulkhead connections.

I've replaced the starter relay, so I have the old one which still works, and I've made 2 10ga wires with 14ga fusible links on both ends to put across the alternator battery and starter relay bolt, but this won't do anything to solve the ignition voltage.

The car turns over but doesn't start, and spark at the coil will jump a half inch gap but it's very orange and not at all blue.

To resolve the ignition voltage supply issues, my immediate thought is to use the old starter relay to create a new ignition voltage feed. I'm thinking that if I wire the BAT post to the BAT post on the new actual starter relay, then wire the G post to chassis ground, and the SOL terminal to the N location in the bulkhead (this is the connection where ignition voltage normally comes back out from the bulkhead), and the original ignition voltage that originally came out of the bulkhead to the I terminal on the relay, I'll have a 'new' ignition supply triggered by voltage coming from the now weak ignition switch. Of course this relys on the ignition voltage from the ignition switch actually being present, so given its unreliability maybe it would be better to just use a manual switch to turn on ignition voltage rather than this relay.

I have a pertronix 3ohm coil that I'm replacing the current can with, so that will allow me to run safely without a ballast resistor.

Mostly I'm just looking for someone to tell me a better idea, or that I'm an idiot. I'm throwing this out there, so any thoughts are welcome.

Here's a diagram I worked up, which does not represent my final plan, and has a ballast resistor in the diagram, but drawing it up helped me track down some of the wiring, in case anyone finds it useful.

This started originally as a thread at http://www.slantsix.org/forum/viewtopic.php?t=53793 but this was starting to go way off topic and become very electrical, so I'm continuing it here.

Image
Author:  oldskoolracer [ Wed Nov 20, 2013 3:04 pm ]
Post subject: 
Im a little confused as to what your looking for... Are you trying to do a temporary set-up just to hear it run, or a semi-permanent solution for it and still drive it around and have things function proper?

The best and safest way is to take your time and replace the damaged parts of the harness. Get a proper coil, install the ballast, make sure the ICM is good, check for fuel and igniton timing... It should start as long as there is power to the coil/icm, timing is set (or at least close to right), and it cranks over... You said the coil sparks, but is weak so start there, maybe just a bad coil. Also double check ALL ground locations. Even if your power supply is good, it means nothing if it does not have a good clean ground path to return. If you want, TEMPORARILY run a wire straight from the batt to a ballast and from there to the coil + and try to start it again, see if the spark is any stronger or not. :wink:
Author:  killnine [ Wed Nov 20, 2013 3:41 pm ]
Post subject: 
Quote:
Im a little confused as to what your looking for... Are you trying to do a temporary set-up just to hear it run, or a semi-permanent solution for it and still drive it around and have things function proper?

The best and safest way is to take your time and replace the damaged parts of the harness. Get a proper coil, install the ballast, make sure the ICM is good, check for fuel and igniton timing... It should start as long as there is power to the coil/icm, timing is set (or at least close to right), and it cranks over... You said the coil sparks, but is weak so start there, maybe just a bad coil. Also double check ALL ground locations. Even if your power supply is good, it means nothing if it does not have a good clean ground path to return. If you want, TEMPORARILY run a wire straight from the batt to a ballast and from there to the coil + and try to start it again, see if the spark is any stronger or not. :wink:
Yes, I need to get the car drivable, but safe, at least temporarily. I have no other vehicle most of the time, and I'm moving the car 2 hours away in a week. I can fix the harness issues over time once I get the car moving.

I have a 3 ohm coil that doesn't require a ballast, so I'll put that in first. I think my first steps are to install the new coil, install the two fusible linked wires from alternator to battery, to bypass charging through the ammeter, and then, disconnect the ignition output from the bulkhead, and connect a wire from the starter relay to the splices providing voltage to the ignition, which is normally connected to the bulkhead to get voltage from the switch. A fusible link in this wire wouldn't be a bad idea either.
Author:  oldskoolracer [ Thu Nov 21, 2013 9:16 am ]
Post subject: 
Well it sounds like you have a start on it at least. I know some people on here might disagree with me but you can run one large cable from the alt to batt instead of 2 smaller ones. On my 78 Volare I have a 4awg charge wire with a maxi-fuse on the battery side, and I replaced and added ground wires to the frame and engine, and an optima red-top. Added 2 fuse panels under the dash and a relay, one is hot at all times, the other comes on with the key in "on" or "acc". Also has HEI, the car starts faster, all the lights are brighter, and I have full battery voltage at all locations, with a constant 14.8 volts while the car is running. Has aftermarket gauges, and a full stereo including a 2000w amp powering the subwoofer, and a 1200w powering mids and highs. Oh yeah, still running an old style 65a alternator 8)

Everything else in the wiring is original, and the acc power for the fuse panel relay is powered off of the old stereo power wire. I know the 78 is a bit different in wiring, including having the bulk head connector inside the car under the dash rather than mounted to the firewall, but overall the systems are the same and wiring is very similar.
Author:  killnine [ Thu Nov 21, 2013 10:59 am ]
Post subject: 
Quote:
Well it sounds like you have a start on it at least. I know some people on here might disagree with me but you can run one large cable from the alt to batt instead of 2 smaller ones. On my 78 Volare I have a 4awg charge wire with a maxi-fuse on the battery side, and I replaced and added ground wires to the frame and engine, and an optima red-top. Added 2 fuse panels under the dash and a relay, one is hot at all times, the other comes on with the key in "on" or "acc". Also has HEI, the car starts faster, all the lights are brighter, and I have full battery voltage at all locations, with a constant 14.8 volts while the car is running. Has aftermarket gauges, and a full stereo including a 2000w amp powering the subwoofer, and a 1200w powering mids and highs. Oh yeah, still running an old style 65a alternator 8)

Everything else in the wiring is original, and the acc power for the fuse panel relay is powered off of the old stereo power wire. I know the 78 is a bit different in wiring, including having the bulk head connector inside the car under the dash rather than mounted to the firewall, but overall the systems are the same and wiring is very similar.
Wow, nice! I don't think there's anything wrong with 1 big wire vs 2 smaller. I think the only point is some people might have an easier time connecting two smaller connections than one big one. Functionally I think it's the same.

My original idea of branching the power off of a relay may be a good one, kind of like what you are doing, but I'm now thinking not so much, because I'm unsure if it really helps the situation any. If I have unreliable power triggering the relay, then the relay becomes unreliable, and defeats the whole purpose. Then again, I don't really know if that's true or not. I may have intermittent grounds or something on my old ignition circuit, and therefore my accessories and everything else on that circuit, so that wouldn't be much of a reliable relay trigger. If it was just a voltage drop without any loss of ground or current, then maybe it would do a decent job of triggering the relay. I think I need to read up more on relays and their function, as it would make it nice to still be able to turn the ignition on and off via the key rather than some other switch or manual intervention.

My current plan is to wire up the new ignition source to the battery terminal, with a fusible link, because at this point I disconnect the battery manually all the time when working on it and when I'm done running it anyhow.
Author:  olafla [ Thu Nov 21, 2013 3:34 pm ]
Post subject: 
Your approach is sound. I became aware of the voltage drop in the main harness, when I measured it when I switched to HEI ignition. I have done more or less the same as you in my Aspen, even if the F-bodies had a better original setup than the A-bodies. See the last post in this thread for my setup:
extra fuse box

You don't have to be concerned about the relay activation current/voltage, relays usually respond to a relatively weak signal.

If you are uncertain about the state of your old main harness inside the car, a setup like the one described, will ensure that you can continue driving, with the lights turned on if necessary, even if the rest of the circuit collapses underway.
Provided it is fused, of course! :D

Olaf

PS
I HATE fusible links! An old link broken in the solder joint, is almost impossible to trace, roadside, in the dark, without tools. Grrrrr!!
Author:  killnine [ Thu Nov 21, 2013 4:32 pm ]
Post subject: 
Quote:
Your approach is sound. I became aware of the voltage drop in the main harness, when I measured it when I switched to HEI ignition. I have done more or less the same as you in my Aspen, even if the F-bodies had a better original setup than the A-bodies. See the last post in this thread for my setup:
extra fuse box

You don't have to be concerned about the relay activation current/voltage, relays usually respond to a relatively weak signal.

If you are uncertain about the state of your old main harness inside the car, a setup like the one described, will ensure that you can continue driving, with the lights turned on if necessary, even if the rest of the circuit collapses underway.
Provided it is fused, of course! :D

Olaf

PS
I HATE fusible links! An old link broken in the solder joint, is almost impossible to trace, roadside, in the dark, without tools. Grrrrr!!
Hey thanks Olaf. Good to know it should work. I like that fuse box, and definitely bookmarked it. If things work tonight I'm going to do something like you have done. Even if I fix the under dash issue, it's still a good idea.
Author:  killnine [ Thu Nov 21, 2013 6:08 pm ]
Post subject: 
Ugh and of course just as I'm ready to spend a little time and try to start her up it gets rainy and cold. Guess I'll just have to wait for a lull in the rain and jump on it! I love cars.
Author:  Aggressive Ted [ Fri Nov 22, 2013 8:28 am ]
Post subject: 
killnine,

I did the mods as you describe and it sure is nice to have plenty of power, especially in the winter months when you really need it!

I followed SL6Dan's advice and used two 10 gauge wires in a conduit running beside the headlight harness. Olaf has point, It is much easier to make up and install. Instead of fuseable link wire or fuses I went with circuit breakers. They tie right into my new Optima battery. You can see some of the photos by clicking on the red link below.
Author:  killnine [ Fri Nov 22, 2013 1:13 pm ]
Post subject: 
Quote:
killnine,

I did the mods as you describe and it sure is nice to have plenty of power, especially in the winter months when you really need it!

I followed SL6Dan's advice and used two 10 gauge wires in a conduit running beside the headlight harness. Olaf has point, It is much easier to make up and install. Instead of fuseable link wire or fuses I went with circuit breakers. They tie right into my new Optima battery. You can see some of the photos by clicking on the red link below.
Oh indeed Ted. I've been reading through most of your posts and information. I also replaced my coil with the pertronix because of them. Now I shouldn't have to worry about the ballast or the two ignition circuits.
Author:  killnine [ Sun Nov 24, 2013 11:58 pm ]
Post subject: 
Well I've got it all wired up. Bought a switch today so it can be easily switched on and off. I also remembered today to disconnect the brown wire from the bulkhead, because that also sends voltage out for the resistor bypass, and I don't need it any more. My no-start issue was due to a couple bent pushrods, which I'm taking care of.

So basically I disconnected the whole ignition circuit from the bulkhead, except for the 'start' yellow wire coming from the ignition switch.

I'll eventually get everything under the dash cleaned up and make sure all my grounds are good. Problems with voltage drop can't be ignored. This definitely helps for now though.
Author:  olafla [ Mon Nov 25, 2013 7:09 pm ]
Post subject: 
Quote:
So basically I disconnected the whole ignition circuit from the bulkhead, except for the 'start' yellow wire coming from the ignition switch.
You also need the 'run' wire from the ignition switch, if you connect to the 'start' wire, the engine will fire, but then die instantly when you release the switch! :D

Olaf
Author:  killnine [ Tue Nov 26, 2013 12:19 am ]
Post subject: 
Quote:
Quote:
So basically I disconnected the whole ignition circuit from the bulkhead, except for the 'start' yellow wire coming from the ignition switch.
You also need the 'run' wire from the ignition switch, if you connect to the 'start' wire, the engine will fire, but then die instantly when you release the switch! :D

Olaf
IGN 1 and IGN 2 are both just full voltage, so as long as I deal with switching this on and off through some other means, I don't need them coming from the ignition switch. That was the whole point of most of what I did, because the circuit after it entered the bulkhead at the firewall was having issues. I still use the key to trigger a start, but IGN1 and 2 are both fed straight from the battery at this point. A toggle switch turns it on and off.
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